1. Field of the Invention
The present invention relates to a paper processing apparatus that performs a predetermined process on a sheet recording medium brought in (referred to as “paper” in this specification) and an image forming apparatus that includes this paper processing apparatus in the body, such as a copier, a printer, a facsimile, and a digital complex machine.
2. Description of the Related Art
Apparatuses called paper processing apparatuses or paper post-processing apparatuses, which are arranged at the rear stage of an image forming apparatus and that perform at least one process among processes such as aligning, sorting, stitching, and folding paper printed by the image forming apparatus, are in widespread use. Such apparatuses typically perform alignment while sorting, stitching, and folding paper. This type of paper processing apparatus usually includes a pair of discharging rollers (upper roller) that discharges paper and a discharge guide plate that rotates so as not to inhibit carrying-in of paper during the carrying-in and so as to surely discharge a bundle of paper during the discharging, for discharging an aligned paper bundle.
For example, inventions disclosed in Japanese Patent No. 4047091, Japanese Patent No. 3284782, and Japanese Patent Application Laid-open No. 2008-030923 are known as such techniques including a pair of discharging rollers and a discharge guide plate. Among them, Japanese Patent No. 4047091 discloses a sheet post-processing apparatus including: a paper conveying unit that conveys a sheet; an upper conveying guide that guides the upper surface of the sheet conveyed by the paper conveying unit and is vertically displaceable; a lower conveying guide that opposes the bottom of the upper conveying guide and that supports and guides the lower surface of the sheet conveyed by the paper conveying unit; an upper sheet ejecting rotating body and a lower sheet ejecting rotating body that eject and convey the sheet at the downstream of the upper conveying guide and the lower conveying guide and that are vertically arranged; an arm member that has the upper sheet ejecting rotating body and is vertically displaceable; a lifting unit that pushes the arm member upward and separates the upper sheet ejecting rotating body from the lower sheet ejecting rotating body; a sheet post-processing unit that is arranged downstream of the paper conveying unit in a paper conveying direction and that performs a process on the sheet stacked on the lower conveying guide; and an interlocking unit that displaces the upper conveying guide upward when the arm member is displaced upward by the lifting unit. The sheet post-processing unit, the upper sheet ejecting rotating body, and the lower sheet ejecting rotating body are arranged downstream of the paper conveying unit in a paper conveying direction in this order.
Japanese Patent No. 3284782 discloses a paper sheet post-processing apparatus for performing a post-process such as stitching and punching on the paper sheets discharged from an image formation section. The paper sheet post-processing apparatus includes: a compiling tray that has at least a paper sheet gathering paddle and a paper sheet aligning plate for aligning the paper sheets discharged from the image formation section; a paper sheet post-processing machine installed at the rear end part of the compiling tray; a loading tray for loading the paper sheets discharged from the compiling tray; and a set discharging roller that discharges the paper sheets aligned (set) by the compiling tray to the loading tray. The paper sheet post-processing apparatus is configured to make one end of the paper sheets on the compiling tray contact with the loading tray. The paper sheets discharged from the image formation section are set and discharged onto the loading tray via the compiling tray regardless of the existence of the post-process by the paper sheet post-processing machine.
Japanese Patent Application Laid-open No. 2008-030923 discloses a sheet post-processing device including: a stacking tray for stacking paper sheets to which image formation is applied; a guide roller for guiding paper sheets to the stacking tray; an alignment member for aligning paper sheets stacked on the stacking tray; a stitching processing unit for stitching the aligned paper sheets; and an ejection unit for pushing up a paper sheet bundle stitched in the paper delivery direction and ejecting the paper sheet bundle from the stacking tray. The guide roller is arranged in the position opposite to the stacking tray. When the paper sheet bundle guided to the stacking tray is ejected from the stacking tray, the guide roller is driven in the direction reverse to the rotating direction at the time of guiding of paper sheets to the stacking tray.
Among them, Japanese Patent No. 4047091 discloses the sheet post-processing apparatus in which a pair of discharging rollers (upper roller) and a discharge guide plate are rotated by a cam positioned below the pair of discharging rollers. Japanese Patent No. 3284782 discloses the paper sheet post-processing apparatus in which a discharge guide supported upward by a spring is rotated by a cam in a direction against the spring. Japanese Patent Application Laid-open No. 2008-030923 discloses the sheet post-processing device in which rotation is applied by a link mechanism provided at the upper side of an opening and closing guide plate.
The invention disclosed in Japanese Patent No. 4047091 configured as described above is difficult to respond to changes in the thickness of paper or a bundle of paper because paper is discharged by the weight of the pair of discharging rollers (upper roller) itself and by alternatively arranging the pair of discharging rollers. Therefore, non-feeding of paper, folded lines, or similar failures may occur. In the invention disclosed in Japanese Patent No. 3284782, the guide is rotated and the discharging roller is pressurized against the spring, and therefore, the load on paper becomes large, and the pressurization on paper becomes unstable. Moreover, in the invention disclosed in Japanese Patent Application Laid-open No. 2008-030923, the opening and closing guide plate is moved by the link mechanism provided at the upper side of the opening and closing guide plate, and therefore, a space is required above the opening and closing guide plate. This results in a large apparatus as a whole, and thus, the demand for downsizing the apparatus cannot be satisfied.
The present invention provides a paper processing apparatus that can be mounted on and discharge paper in a limited space, that is, the body of an image forming apparatus, has stable conveying force regardless of the thickness of paper and of a bundle of paper, and can perform paper process without damaging paper.